Allow to control if tokens are always, optionally or never requested

Problem/Motivation

The feature to allow users to store their payment data is interesting but not always what's desired. Sometimes you might want to never offer that, or in other cases, always, even for anonymous users. Our case case is then setting up subscriptions in a second step based on that token, so it won't be stored in Drupal, but we use it in our own code afterwards.

Steps to reproduce

Proposed resolution

Convert the current checkbox to a select with 3 options: Never, Ask, Always.

Remaining tasks

User interface changes

API changes

Data model changes